The AC voltage waveform of square wave inverter output is square wave. This type of inverter used by the inverter line is not exactly the same, but the common feature is the simple line, the use of power switch tube number is very small. The design power is generally between hundred watts and KW. The advantages of square wave inverter are: simple circuit, cheap price, convenient maintenance. The disadvantage is that the square wave voltage contains a large number of high harmonics, in the core inductance or transformer load with the electrical appliances will produce additional losses, the radio and some communications equipment interference. In addition, this kind of inverter is not wide enough to adjust the pressure range, the protection function is not perfect, the noise is relatively big and so on disadvantage.